It adds an allure of exclusivity hence allowing developers to charge higher prices.
I have to say that I am glad I do not live in one; I would miss the passing Carol Singers/Trick and Treaters/window cleaners/burglars pretending to be window cleaners/have- you -thought -about -switching -your -power supply- provider -and if you don't -we'll -fiddle- the -forms -anyway salesmen/kids seeking urgent medical assistance for injured hedgehogs(seriously)/people who knock at midnight saying they have lost their way( next time will refer to JW's)/the Betterware people/electoral canvassers/can you take in this parcel please people etc.
I used to live on the 4th floor of a block of flats and whilst not gated the stairs were enough to keep out such folk so now that I live in a house I am regularly reminded of lifes great tapastry on a daily basis.

Not quite the answer to the question asked but had fun writing it anyway.....